The irradiated targets were placed 3 cm away from the front surface of the detector.
The absolute efficiency was calibrated with one \(^{152}\) Eu and six monoenergetic sources (\(^{137}\) Cs, \(^{241}\) Am, \(^{54}\) Mn, \(^{88}\) Y, \(^{104}\) Cd, \(^{65}\) Zn).
The sources were placed at the same position as the targets.
The absolute full-energy peak efficiency curve was described using the EFFIT program in the Radware [1]} package.
The efficiency curve was further corrected for the summing coincidence effect by a dedicated GEANT4 simulation [2]}.
The impact of geometric acceptance due to the size of irradiation target, is estimated to be less than 1%. This effect is much smaller than the statistic error.
